Both of the teachers you have mentioned are great. These teachers had taken the way to teach biology to a pioneering level. Now you can follow both of them. But if you have to compare, then as per my experience I would say Dr. Geetendra Singh focuses more on fundamentals and his explanations are more likely to remember due to his amazing method of explanation.

I would say if you can try both of them and go for the one you feel the best for you. My experience can't be always the same with yours. So its better to discover yourself whats the best for you. I suggested my opinion based on my experience only.

I hope this answer helps. All the very best for your future endeavors!